In general, a resectscope is used for transurethral resection (TUR) and transcervical resection (TCR). The resectscope mainly includes an optical scope (sometimes simply called scope), which is an endoscope for observation, and an electrode unit for resecting living body tissue.
As the resectscope, for example, Japanese Examined Utility Model Registration Application Publication No.4-45694 discloses an electrode for rigid scope surgical instrument having a rigid heat-resistance member between a distal end portion of an electric insulative member and an elemental wire. The rigid heat-resistance member is in contact with the periphery of the elemental wire. Thus, burns of the electric insulating member can be prevented.
When the resectscope is used for resecting the prostate, for example, D-sorbitol which is insulating transparent liquid as a perfusion fluid may be supplied for expanding the inside of a narrow cavity. Thus, the cavity is expanded, and a sheath of the resectscope can be inserted into the cavity.
Then, the surface of a lesion is observed by using a scope located within the sheath. At the same time, high frequency current passes through a treating electrode of an electrode unit located at a distal end portion opening of the sheath. By discharging, current flows from the treating electrode to an external electrode located outside of a body through the liquid filled within the cavity. Then, the operating portion is manipulated to move the treating electrode back and forth for treating the lesion.
Here, because the perfusion fluid filled within a cavity is an insulative liquid, the distribution of current traveling from the treating electrode to the external electrode can be prevented. Thus, more efficient treatment can be performed.
However, when a treatment is performed by filling an insulative liquid within a cavity, and when the treating time is longer, the liquid is absorbed into a blood vessel, which may have bad influences on a human body. Therefore, the operation time is limited.
In order to overcome the problem, a physiological saline, which is a conductive liquid, may be filled within a cavity as a perfusion fluid. However, when the conductive liquid is filled within a cavity, current to flow from the treating electrode to the external electrode disperses through the liquid. Therefore, discharging does not occur on a lesion, thus disadvantageously cannot achieve effective treatment.
Thus, Japanese Unexamined Patent Application Publication No. 2000-201946 discloses a resectscope apparatus including a treating electrode and a return electrode. The treating electrode is located in the vicinity of a long, narrow and hollow sheath distal end portion to be inserted into a body cavity filled with a conductive liquid. The treating electrode treats a body tissue by using high frequency cauterization current. The return electrode is provided within the conductive liquid and receives current from the treating electrode. An insulating portion is provided on at least a non-contact surface of the body tissue of the treating electrode. Thus, high frequency current supplied to the treating electrode within the cavity filled with the conductive liquid does not leak from the insulating portion on the non-contact surface of the body tissue to the liquid. The high frequency current is efficiently discharged from the body tissue contact surface of the treating electrode which is in contact with a body tissue. The high frequency current flows to the return electrode.
However, as shown in FIG. 12, in order to prevent high frequency current supplied to a treating electrode 501 from returning to a return electrode 504 not through a body tissue 502 but directly through a conductive liquid 503, the resectscope apparatus according to Japanese Unexamined Patent Application Publication No. 2000-201946 includes an insulating portion at least on a body tissue non-contact surface of the treating electrode. However, the insulating portion on the non-contact surface of the body tissue is complicated in structure. Therefore, the manufacturing is disadvantageously difficult in effect.
The present invention is made in view of the above-described problems. It is an object of the present invention to provide a resectscope apparatus, which has a simple structure and is inexpensive, for treating a lesion effectively without adverse effects of an insulative liquid on a human body and without limitation on an operation time.